The killer sea waves known as tsunamis are so quiet in their approach from afar, so seemingly harmless, that until recently their history has been one of the surprise attacks. Out in the middle of the ocean, the distance between tsunami wave crest can be 100 miles and the height of the waves no more than three feet. Mariners can ride and suspect nothing. At the shoreline, the first sign is often an ebbing of the waters that leaves fish stranded and slapping on the bottom. However, this is not a retreat but rather a gathering of forces. When the great waves finally do strike, they rear up and batter harbor and coast, inflicting death and damage. These seismic sea waves - or tidal waves, as they are sometimes called - bear no relation to the moon or tides. And the word 'tsunami,' Japanese for 'harbor wave', relates to their destination rather than their origin. The causes are various: undersea or coastal earthquake, deep ocean avalanches,' or volcanism. Whatever the cause, the wave motion starts with a sudden jolt like a whack from a giant paddle that displaces the water. And the greater the undersea whack, the greater the tsunami's devastating power. In 1883, Krakatoa volcano in the East Indies erupted, and the entire island collapsed in 820 feet of water. A tsunami of tremendous force ricocheted around Java and Sumatra, killing 36,000 people with walls that reached 115 feet in height. In 1946 a tsunami struck first near Alaska and then, without warning, hit the Hawaiian Islands, killing 159 people and inflicting millions of dollars of damage. This led to the creation of the Tsunami Warning System, whose nerve centre in Honolulu keeps a round-the-clock vigil with the aid of new technology. If seismic sea waves are confirmed by the Honolulu centre, warnings are transmitted within a few hours to all threatened Pacific points. While tsunami damage remains unavoidable, lives lost today are more likely to be in the tens than in the thousands. Tsunamis have been deprived of their most deadly sting-surprise.
1. According to the passage, seismic sea waves{#1}
A. originate far from the place where they strike
B. are easily detected by fishermen
C. are named 'tsunami' for the origin of the wave in the harbor
D. are called tidal waves because of their relation to the moon
5. The author's main point in the passage is that{#5}
A. there is little possibility of avoiding tidal waves once they are in motion
B. seismic sea waves today are carefully monitored and cause less damage than in the past
C. tsunami can do little damage when they strike
D. we need better equipment to track the movements of tsunamis